Modeling of work systems occurs for all sorts of reasons. Requirements need to be expressed. A pre-existing situation may need to be charted and analyzed. Early design decisions may be captured using architecture principles. Detailed design may be worked out. We all regard these activities as essentially being forms of modeling. In the work systems modeling library, we consider work system engineering from a modeling perspective. In the field of work system engineering, a whole plethora of modeling methods is available to system engineers and architects. Each of these methods can be used to model some (aspects) of a domain related to an existing and/or a planned work system. The aspects may refer to requirements, architecture, design, processing, data, etc, etc. In other words, these methodes are essentially all intended to model different aspects of work systems and/or their context. The aim of the work systems modeling library (WSML) is to bring together methodical knowledge concerning the modeling of work systems.